1. Field of the Invention
The present invention relates to a liquid discharge recording head for printing on a print medium by discharging liquid droplets from a discharge port, a liquid discharge recording apparatus on which such liquid discharge recording head is mounted, and a method of producing a stopper member for the liquid discharge recording head.
2. Related Background Art
The conventional liquid discharge recording head is provided with a carriage reciprocating in a direction substantially perpendicular to the conveying direction of a recording medium, and the liquid discharge recording head is mounted on such carriage.
The liquid discharge recording head is principally composed of a liquid discharge portion for discharging liquid from a discharge port thereof, thereby executing recording on a recording medium, and a liquid reservoir chamber containing the liquid to be supplied to such liquid discharge portion. In an ordinary type, a liquid discharge recording head is provided integrally with the liquid reservoir and mounted replaceably on the liquid discharge recording apparatus.
Such a liquid discharge recording head is not designed for liquid refilling, but is disposed of when the initial supply amount of liquid is exhausted and a new liquid discharge recording head is mounted on the scanning carriage. Consequently such a configuration is associated with a relatively high running cost if the liquid discharge recording head is replaced frequently.
On the other hand, for reducing the running cost, a configuration can be used in which the liquid reservoir is separated from the liquid discharge recording head and only the liquid reservoir is replaced when the liquid is exhausted. Also, another configuration can be used in which the liquid is supplied from an external liquid reservoir, positioned outside the liquid discharge recording head, to such liquid discharge recording head.
The configurations of the liquid discharge recording head can be classified, from the standpoint of liquid replenishment, into 1) a configuration in which the liquid reservoir is contained within the liquid discharge recording head, 2) a configuration in which the replaceable liquid reservoir is mounted on the liquid discharge recording head, and 3) a configuration in which the liquid is supplied from the remote liquid reservoir to the liquid discharge recording head, for example, through a tube member.
However, in any of these configurations, the interior of the liquid discharge recording head is maintained at the atmospheric pressure or at a negative pressure, in order to prevent liquid leakage from the liquid discharge recording head.
In the following, the features of the negative pressure generating means in the aforementioned liquid replenishing configurations of the liquid discharge recording head will be explained.
In the liquid discharge recording head containing the liquid reservoir, negative pressure generating means is generally provided in the liquid reservoir in order to maintain a negative pressure therein. The negative pressure generating means employable in such configuration can be, for example, a type for absorbing liquid (liquid absorbing type) or a mechanical type.
The liquid absorbing type has a configuration of maintaining the negative pressure by utilizing the capillary force of a porous liquid absorbent member such as polyurethane foam and retaining the liquid in such liquid absorbent member. On the other hand, the mechanical type has a configuration of maintaining the negative pressure in the liquid reservoir by contracting a flexible wall portion, for example, utilizing the repulsive force of an elastic member.
In the following, the liquid discharge recording head having the replaceable liquid reservoir will be explained. In such head, the negative pressure generating means of the liquid absorbent type is generally employed. Thus, the liquid in the reservoir is prevented from dropping from the connection aperture thereof by the liquid retaining power of the porous liquid absorbent member or the like.
In the following, the liquid discharge recording head relying on the liquid supply from the external liquid reservoir will be explained. In such head, the negative pressure generating means can be the liquid absorbent type, the mechanical type, or a type in which the liquid level of the external liquid reservoir is positioned lower than the discharge port face of the liquid discharge recording head to generate a water head therebetween, thereby maintaining the interior of the liquid discharge recording head at a negative pressure.
For discharging liquid droplets from the liquid discharge recording head, there are already known, for example, a configuration of discharging a small liquid droplet from a discharge port utilizing thermal energy generated by an electrothermal converting member, and a configuration having a pair of electrodes to discharge a liquid droplet under deflection. Among these, the ink jet recording head utilizing thermal energy for liquid droplet discharge is capable of recording at a high resolution because the liquid discharge portion (discharge port) for discharging recording liquid to form a flying liquid droplet can be arranged at a high density. Also, this type of recording head is capable of easily making the entire head compact, and, therefore, has already been commercialized.
The ink jet recording head utilizing thermal energy for discharging recording liquid is provided with plural sets of discharge ports (orifices) for discharging liquid, a liquid flow path communicating with the discharge ports and an electrothermal converting element positioned corresponding to the liquid flow path. The recording head is constructed to execute the recording operation by supplying the liquid in the liquid flow path with discharge energy from the electrothermal converting element (for example, thermal energy for causing film boiling in the liquid), thereby discharging the liquid as a liquid droplet from the discharge port.
In the following, with reference to FIG. 15, the general configuration of the above-described ink jet recording head will be explained.
In a conventional ink jet recording head H shown in FIG. 15, an element substrate (heater board) 1107, provided with a heat generating element (heater) 1106 constituting an energy generating member for generating energy to be utilized for liquid discharge, is die bonded to a support member 1110 composed, for example, of aluminum or ceramics. On the support member 1110 there is adhered, in addition to the element substrate 1107, a wiring board 1108 for electrical contact with the main body of the recording apparatus, and the element substrate 1107 and the wiring board 1108 are electrically connected by wire bonding or lead bonding.
The element substrate 1107 is provided therein, in addition to the heat generating element, with a driving shift register and wiring patterns, which are formed in advance in the element substrate 1107 by silicon processing technology, together with the heat generating element 1106. The wiring board 1108 is also provided with a contact pad (not shown) for electrical contact with the main body of the liquid discharge recording apparatus.
A top plate 1100, formed, for example, by injection molding of a resinous material so as to be integral with an orifice plate 1101, is adjoined to the surface of the element substrate 1107 and the front end faces of the element substrate 1107 and the support member 1110. In the orifice plate 1101, there are formed fine discharge ports 1102 for discharging liquid droplets. In the adjoined portion of the top plate 1100 with the element substrate 1107, there are formed recesses constituting liquid flow paths 1103 communicating with the discharge ports 1102 and a recess constituting a liquid chamber 1104 communicating with the liquid flow paths 1103. In the top plate 1100, there is also formed a recording liquid supply aperture 1105 to communicate with the liquid chamber 1104, thereby supplying the recording liquid thereto.
The top plate 1100 is fixed to the element substrate 1107 by unrepresented pressing means such as a spring or adjoining means such as adhesive, and the liquid flow paths 1103 and the liquid chamber 1104 are defined by the wall portion of the top plate 1100.
The top plate 1100 need not necessarily be formed integrally with the orifice plate as explained in the foregoing, but there may also be adopted a configuration in which the orifice plate 1101 is formed separately from the top plate 1100 and is later adjoined thereto.
In the latter configuration in which the orifice plate 1101 is formed separately from the top plate 1100, there is employed a method of aligning the discharge ports 1102 on the orifice plate 1101 with respect to the liquid flow paths 1103 formed by pressed contact of the element substrate 1107 and the top plate 1100, and then adjoining the orifice plate 1101 to the top plate 1100 and the support member 1110. Such method has an advantage that the material for the orifice plate 1101, requiring durability, can be selected arbitrarily.
On the other hand, in the former configuration in which the orifice plate 1101 is integrally formed with the top plate 1100, since the discharge ports 1102 are formed in communication with the recesses constituting the liquid flow paths 1103, there can be attained excellent productivity as the liquid flow paths 1103 can be formed by simple mechanical pressing of the top plate 1100 and the element substrate 1107.
In case of the latter configuration, the top plate 1100 is formed, for example, with silicon, ceramics, or resinous material, while the orifice plate 1101 is formed, for example, with silicon, resinous material, stainless steel (SUS), nickel, or ceramics by an ultrafine working method such as laser working, electroforming, molding, anisotropic etching, or pressing.
The ink jet recording apparatus employing the above-described ink jet recording head H is principally used as a color printer by connecting to a word processor or a personal computer, and is also utilized as a driving engine for a facsimile apparatus or a copying apparatus.